Apparatus for treating iron and iron alloys



Dec. 18 1923. 1,478,366

w. H. FISHER ET AL APPARATUS FOR TREATING IRON AND IRON ALLOYS Filed May 18, 1920 7 I I I 1 INVENTORS, Mllzmgblwadfifler "-lPeirr (Am/Jam;

. C ATTORNEY Patented Dec. l 1923. I

entrain stares aaranr or WILLIAM HOWARD EISHER, 0F LOS ANGELES, AND PETEROHAMBERS, 0F BEDONIDQ area.

BEACH, CALIFORNIA.

arrnnarusror. rnna'rrn men AND rnon ALLOYS.

Application filed May 18, 1920. Serial No. 382,290.

To all whom it may concern:

Be it known that we, WILLIAM HOWARD FISHER and PETER CHAMBERS, citizens of the United States, residing at Los Angeles and Redondo Beach, respectively, in the county of Los Angeles and State of California, have invented new and useful Improvements in Apparatusfor Treating Iron and Iron Alloys, of which the following is a specification.

This invention relates to apparatus for treating iron and iron alloys. It has for an object the provision of a suitable furnace which utilizes aparticular liquid hydrocarbon which will not oxidize the steel used in the furnace. Another object is to provide a furnace using a liquid hydrocarbon which will perform the impregnating proci a bluish flame.

change in the bluish color, as well as the ess or make the surface of-the steel more dense with carbon in a shorter'period of time than heretofore, and which impregnating process will be performed with uniformity, will leave no soft spots in the metal and reduce the costin operation.

Preferably We use a particular liquidficial means, as now used, to know. at a glance the degree of carbon being absorbed by the steel in the interior of the furnace.

In practicing the invention we Erovide a special hydrocarbon oil which is ed into a suitable retort at a pro-arranged speed. This retort connects with the interior of a cylindrical casing provided with perfora-' tions, which latter casing is arranged within a work-holding retort.

Suitable heating means heats the retort and in so heating gasifies the liquid and the gasified liquid passes through the perforations and contacts with whatever work may be within the work-holding retort. Gas is .;allowed to escape through a vent in the cover of the retort after the carbon has been taken from 7 same. and the gas as it escapes burns with The particular color or height which the flame reaches, indicates the rarest materials as charred leather, powdered bone,

cyanide of potassium, wood and animal charcoal, prussiate of potash and other materials consisting of mixtures of carbonaceous materials and certain cyanides and nltrates. nated with carbon are first'packed ina suitable box after a layer of casehardening material has been placed upon the bottom of said box, the thickness of the layer depending on the size of the pieces to-be hardened. Obviously in order to properly caseharden a metal it is necessary that the surfaces of the parts should be in direct contact with the carbonaceous material, and if the parts should happen to touch one another it is quite likely that the parts that touch will be softer at the space where they "are in contact. It has been found that if there is not enough carbonizing material in the box the Work is also liable to have 'soft spots. It has been found impossible to properly impregnate steel or make' it more-dense where considerable depth of carbon is required by packing the .articles with bone or charcoal in an iron box and sealing on ;'the cover. This is due to the fact that only-a certain amount of carbon is present, and the longer the work is baked, the more there will be in the steel. VVh'en an e uilibrium is established no more carbon wi l penetrate the metal," and to obtain a greater depth, the work must iron boxes packed with'carbonaceous' mate- 'rial, and that such processes have been developed by Giolitti and by the American The steel articles to be impreg Gas Furnace Company. The Giolitti process consists essentially inpacking the work;

with wood charcoal in a cylinder and when heated to carbonizing temperature a current of carbon dioxide is injected into the cylin-- der. The American gas furnace process or method consists in using gas as a carbonizing material and placing the work in a small revolving, properly heated, cylindrical retort into which the carbonizing gas is injected under pressure. F rom the gas the work-absorbs the volatile carbon.

It is obvious that a furnace of this type using a carbon gas would be less expensive in operation than the old method of first packing the articles to be impregnated with carbon, as at least three or four operations would beenti'rely done away with." It has been found thatthe use of carbon monoxide while capable of rapid penetration,v has an oxidizing effect on steel, and is liable to form a scale that will spoil small work which cannot afterwards be ground. This oxidizing effect is more pronounced in chromium and-"manganese steels. Casehardening is mostly performed on small articles which must have a perfectly hard surface,

and yet be of such internal structure that there is no chance of breaking them when in use.

nace method, while this ensures an even distribution of heat, still the revolving process is liable to dump the different articles within the retort upon each other and if the articles should happen to be gears, to possibly break the teeth of same. "With the idea of overcoming the objections now incident to furnaces of this latter type, the

' inventors have constructed a novel form "of oven which utilizes a particular hydrohydrocarbon is capable of being sd a'djusted carbon fluid which will not oxidize the steel. thus spoiling small work. The interior of the work-holding retort is at all times dry; that is to say, water is not formed within theretort upon the heating of the gas, as is ordinarily the case; in fact, the presence of water is highly disastrous in furnaces of this form. Likewise the gas used does not have an oxidizing effect on thealloyed steels. The entire furnace with its, liquid that one attendant can readily perform all to. Furthermore, the apparatus is simple in design and readily accessible.

"It will be"-f -'u derstood that the use of this hydrocarborrggl iquid and this furnace is for performing the casehardening process only, and does not refer to the quenching or the tempering process that is necessary aften the steel has been impregnated with carbonf The furnace is made of such a size that it gives a uniform heat through out and performs its work more rapidly and more uniformly than is possible with any known process on the market today. The carbon removed from this hydrocarbon liquid will find its way into slots, holes and cavities which would not under ordinary circumstances receive the carbon from the granulated bone or any other conjunction with efficiency speed and expediency and general adaptability.

The invention consists in the novel and useful means hereinafter disclosed and finally pointed out in claims.

It will be understood that many varia tions in detail may be made in departure from the specific definition of the process as well as the apparatus about to be disclosed.

The improved process for treating iron and its alloys is claimed in a divisional application filed October 13, 1920, Serial No. $16,657, and the improved composition for treating iron and its alloys was filed October 13, 1920, Serial No. 416,658 which application was allowedon July 19, 1921.

. In the drawing:

Figure 1 is a fragmentary elevation, certain parts being shown in section of an improved furnace used in connection with a certain liquid hydrocarbon for caseha-rd' ening steel, taken on the line m m Figure 2; Figure 2 is a fragmentary bottom View of the device shown in Figure 1, and taken on the line ac 'a2 Figure 1, and looking in the direction of the appended. arrows; and e 1 Figure 3 is a cross sectional view of the vice shown in Figure 1 and taken on the fine m m Figure 1, and looking in the direction of the appended arrows. the operations necessary and incident there- Correspond ng parts in all the figures are designatedby the same reference characters.

Referring with particularity to the drawing, A designates a furnace of which B is aeraeee the outer casing wall, Cheat resisting means,

i D a work-holding retort co-axially arranged hydrocarbon within the perforated cy drical wall member,--all of which elements are used in practicing one embodiment of the inventio The furnace A is so constructed that all 1 parts-of the furnace are readily accessible.

The furnace consists essentially in the outer cylindrical casing B provided with a cover member 1*anda base member 2. Within the outer casing B are arranged fire brick or other heat-resisting material C. This heat resisting material 0- is made in segments as shown in Flgure 3. This particular construction overcomes any tendency for the furnace to crack or bulge due to excessive {heat or exces'slve' cold incldent to cooling.

Intermediate the outer periphery of the heat-resisting means C and the casing B is a fibrous substance 3 which will not conduct heat. The end portions 1 and 2 are likewise provided with heat-resisting means C, the cover lend the base 2 holding the heat-resi'sting means C in position. In orderto ensure the casing B maintaining its form a flanged rim 4 is provided at its upper end as at 5 and held in position thereto by bolt members or screws 6. The heat-resisting means C is' annular in form in order to accommodate the work-holding retort D, as shown in the drawings. The base member 2 is likewise annular in form and is provided with a downwardly directed flange 7 at its outer edge, which flange isperforated to accommodate bolts 8'for holding the outer casing B to said base and flange. Certain of the fire brick or heat-resisting elements C are provided with, semi-conical perforations 9 which likewise extend through the nonconducting heat element 3 and the outer casing B. Disposed Within a portion of this perforation 9 is a pipe 10 connecting with the source-of supply of whatever fluid is to be burned to-heat the furnace. The perforation 9 is purposely made in the form shown in Figures 1 and 3 so as to allow for an expansion of the gas as it is discharged fromthe opening in the pipe 10. The work-holding retort D which likewise acts as a mufile is disposed within the annular space formed by the members C and supported upon the base member 2. The work-holding retort l)- is preferably cylindrical in form and has an end portion as at 11 slightly beveled as at 12 on the outer peripheral edge thereof. The lower annular heat-resisting means C is t5 likewise beveled as at 13 on its inner peripheral annular edge. The heat-resisting element C, as well as the work-holding retort D are made this way'in order that there may be a close' cooperation with their respective edges in order toensure a close fit with little or no loss'of gas. or heat. The base member 2 is likewise, provided with a flange 14 in order to aid in retaining the work-holding retort D in position upon same. Reference tothe figures will show that there is a spaced portion 15 existing between the work-holding retortD and the inner peripheral surface of the heat-resisting elements C. Combustion of gases used in heating the furnace occurs in this spaced portion 15. a

The means Gr'used in conducting gas to theinterior of the furnace comprises a series of interrconnecting pipe members 16 joined together by elbows, as shown in the figures. Referring to Figure 2 it will be noted that one portion of the means G communicates with an air supply and the other portion with the source/of gas supply. The part that ordinarily is used in forcing air within the pipe members 16 is associated with a blower so as to give the necessary oxygen content to the gas, as well as to create a hot flame within the space 15 of the furnace A. It is customary to utilize an expansion tank in order to get a constant air pressure. Otherwise the pulsation from the blower will affect the heat in the furnace. However, in the particular construction of the furnace shown, it is not absolutely necessary to use the expansion tank, as the perforation 9 and the space 15 act to a certain extent asan expansion chamber.

The top 17. of the work-holding retort D is provided with a U-shaped or flanged cover member 18, which cover member is provided with a'centrally located vent 19. The cover is likewise provided with gripping ring brackets 20, so that a rod might be run through the perforations 21 'in said ring brackets 20 and the cover 18- removed from the end of the work-holding retort D in order to insert work or to remove work from the interior of said retort D. Supported upon the base member 2 as at 22, is a cylindrical casing E having one end as at 23 circumferentially and outwardly flanged, which flanged portion acts as a foot means for rigidly holding the cylindrical casing E 29 is a protecting spaced plate 30 supported upon legs.31. A side member 32 of the bucket-shaped element 28 has its end as at 33 beveled as shown at 34, and the beveled portion rests upon a correspondingly beveled portion 35* on the inner peripheral annular edge of the base member 2, so that the member 28 may be always retained in a definite I(glose fitting engagement with the base mem- A plate member 35 covers the open annular portion of the base member 2 and likewise the open interior portion of the bucketshaped member 28, and is held in relation to the base member 2 by means of stay bolts 36. The member 35 is provided with a circumferential lug 37 which forms with the edge to which it is joined, flanged portions 38 and 39, which flanged'portion 38 cooperates with the inner peripheral annular wall of the base member 2. Likewise the lug 37 is provided with perforations at certaindistances in order to accommodate the stay bolts 36. The member 35 is internally chambered as at 40 to accommodate a cylindrical member 41, and the chamber wall portions 40 of the member 35 are made at a convergent downward angle while the end portions-as 42 of the member 41 are correspondingly angled or beveled so as to form a close fit with the side walls of the chambered portions 40. Centrally located and communicating with the interior of the member 35 is a perforation 43. Located externally of the furnace A and joined to the casing near one end as at 44 is a bracket arm 45 held in position to the casing B by means of a bolt 46. A portion of the bracket 45 as at 47 supports thereon a sight feed reservoir F of any standard form. Communicating from the interior of the sight feed reservoir F is a fluid conducting pipe 48. Across head 49 joined to the pipe 48,,has one of its terminals as 50 communicating with the perforation 43 and with .theinterior of the member 41. The oppositely directed portion 51, that is, the portion opposite the terminal 50 is provided with a valve cock 52, and a terminal 53 directly opposite the entranceof the conducting means 48 is provided normally with a cap 54.

The furnace is supported from the ground or flooring by means of a. plurality of leg members 55 which are joined to the base 2 and held rigidly thereto.

The operation is as follows:

A liquid hydrocarbon is placed within the sight feed reservoir F and a control valve handle 56 is so set that a predetermined quantity of said hydrocarbon fluid will dro past the sight 57 and intothe pipe 48 and thence fill the container 41. The handle 56 is so set that the liquid hydrocarbon will not overflow its container 41. A plate 58 shown by dotted lines in Figure 1 covers an opening 58 provided in the members C. When eam the source of gas supply is turned on by means of a valve cock 59 and the air through a valve cock 60 is connected with a blower or other suitable element, said gas may be ignited within the space 15 by opening the plate 58. The-particular construction of the perforation 9 gives the gas and "the air a whirling effect within the space 15 and consequently there is a solid mass. of flame surrounding the work-holding retort D. The heat from the gas is communicated through the walls of the work-holding retort D and thence through the walls and perforations of the member E and finally to the fluid contained within the. member 41. This heat causes the hydrocarbon fluid to vaporize and pass upwardly through the hole 29 in the bucket-shaped member 28 and from a vaporous stage it passes through perforations 24 and 27 in the form of a gas into th work-holding retort. The perforations are preferably made small so as to retard the passage of the gas as much as possible. The gas completely fills the Work-holding retort D and contacts with the work supported upon the cover plate of the member E. As the carbon is constantly removed from the gas and unitin with the steel one of the products of said gas, which is hydrogen, passes upwardly through the vent 19 and 15 there ignited and burns with a pale flame. As is before explained, the particular color of this flame indicates the condition of the carburizing of the steel within the retort. It is customary to note. temperature variation by inserting a thermo-couple or by focusing an optical yrometer successively in different parts of t e furnace, all of which is unnecessary in the present furnace. It has been found that very little or no residue of carbon is left Withinthe retort, after the carburizing operation has been performed; nor are the perforations 24 or 27 completely filled with carbon deposits after a carburizingfoperation.

he work such as gears, axles, etc., 1s stacked upon the cover plate 26 of the mem ber l9 and the plate 18 then placed in position covering the work-holding retort. Ordinarily the carburizing operation requires some twelve hours of time, but with this device it has been found that it will perform the same amount of work in from' carbon fluid used contains little or no oxygen j and the oxygen of the atmosphere is not per mitted to come into contact with the work actual carburization is due to the hot gases which are either liberated by the casehardening compound or formed by the reaction between the occluded air and the carbon. It is also Well-known that the active casehardening reagent is a gas 'or a mixture of gases and that even when a powder is used that it is the gas liberated from the hot powder and not the solid itself that performs the Work. Consequently the use ofa particular liquid hydrocarbon which is utilized in this furnace readily performs its work in a most efiicient and quick manner without waste.

As to the reason why this gas does not make deposits of carbon within the perforations 24 and 27 or why it does not oxidize the steel, or why it has no oxidizing effect on chromium and other alloyed steels, is not known by the inventors.

Reference to Figure 1 shows thatv the hydrocarbon fluid may be readily drained from the member 41 by turning the valve "cook 52 and closing the handle56 which controls the sight feed reservoir. The plate 30. provided with the legs 31 covering the hole 29 of the member 28 is placed there for the express purpose of preventing any foreign substance, if any vthere be, from fall- 1ng upon the liquid hydrocarbon contained within the member l1 and forming a surface coating upon said liquid that might prevent its ready vaporization. If it were desired to clean the internal parts of the furnace a removal of the stay bolts 36 would allow the plate 35 to be removed from the base member 2. This will allow the cross head .28 likewise removed; If. desired.- the work-. holding-retort Djgc'ould b'edrawn through the annular' space'formedby;the, heat-resisting elements G and-C and a new work-holding 49, toi be released i from the f perforationi43 7 and the plate 3 5and the member 411*v with- ,"drawn from'p'osition. 'I "h us the inte'r-ior of I n the .bucket'shaped; member 28"fimi ght' be p cleaned. 'Byremo'ving the 'cov'er1 8the cy- -hndricalmember-Emight be drawn through i v Wall-spaced from said heat-resist1ng wall,

the. workwholding, retort D and the .member 'r'etort placed therein. I Thus it will be ob for renewal orfor .repairsz -i 1 said hydrocarbon fluid.

tar turpentine 20% and 'linseed- 40%, will most efiiciently when, ga sifie'd carburize or caseharden steel. combina- I tion of these particular elementsto form the hydrocarbon fluid will perform all the rune tions that have been above 'attrfibutedto It is manifest that many variations and"- changes may be made with respect to the I disclosure of the foregoing furnace such asreversing the parts within the workeholding retort D so that the liquid hydrocarbon might be injected through the top of the retort and the gas allowed to".work down wardly through the interstices'of the' work therein ;-all of the above changes,- it being understood, may be made within afair interpretation of the invention. p,

Havin thus disclosed our inventionywe' claim and 1. A furnace, comprising anouter-wall of refractory material, an innerstationary retort wall spaced therefrom, said walls;

desire to secure by Letters Patent:

forming between them a continu0us'-comf;

bustion space, means for su'pportin com-j bustion in said combustion space, w ereby said retort wall is heated; and; means for supplying a hydrocarbon fluid Lathe-spaceconfined by said retort wall; said lastnamed means comprising means for initially 1 0??- ing said hydrocarbon fluid.

2. A furnace for carbonl'z'ing retort so that it gasifies under influence Off the heat present for application to the metal steel and like metals, including a work-holding re-"- there being means associated Iwith' the retort for allowing the resi d1 1e' gas-fromwhich carbonhas been removedto passto the} exterior of the furnace, andburn as'lt escapes, and by observation ofvthe combustion determine the proportion of carbon beingcombined With the metal, and means for regulatingthe flow of the hydrocarbon fluid" into the retort, whereby the carbonizingj op eration' may be regulated as indicated by the combustion of the residue gas.

'A'furnace for carbonizing steel-and like 1 15 metals, meludin-g anouter casing, abase and top member, each' of which-1s prov ded with {a' central opening, detachablyjoined toflsaid casing; a heat-resisting" wall wi thifn said outer casing,- "an inner work-holdingretort said 'la'sftjna'meid wallsforming between'them.

a conti.nuou's goornbustionfspace'; means f supportingcombustionll in -sa 1d, 'combust1on '--.space so as to heat articlescontained with n the work-holding retort, and. means for 5mpservcd that-allfparts are'readily accessible plying ahydrocarbonfluid'to'the space con;

fined by said {work-holdingretort;

4.; A furnace for carbonizingsteel and like metals, including amouter casing, said casing having. raj-curved outer surface, an -annular.

base and top member for said casing, means for detachably joining said base and top members to said casing, walls composed'of non-heat conducting material disposed ad jacent the inner surface of the casing, an inner work-holding retort spaced from said non-heat conducting Wall, said retort wall and said non-heat conducting wall forming between them a continuous combustion space, means for supporting combustion in said combustion space, and means for regulating the heat within said combustion space; means likewise being provided for supplying a hy drocarbon fluid to the space confined by said work-holding retort.

5. A furnace for carbonizing steel and like metals, including a curved outer'casing, an annular base member and top member detachably joined to said casing, a portion of the inner edge surrounding the annular opening in said base being beveled, segmental walls composed of non-heat conducting material disposed adjacent the inner surface of the casing, annular segmental walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding retort wall spaced from said non-heat conducting walls, said workholding retort wall and said non-heat conducting walls forming between them a continuous combustion space, means for supporting combustion in said combustion space whereby said work-holding retort wall is heated, and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort.

6. A furnace for carbonizing steel and like metals, including a curved outer casing, an annular'base member and top member detachably joined to said casing, a portion of the inner edge surrounding the annular opening in said base beingbeveled, segmental Walls composed of non-heatconducting material disposed adjacent the inner surface of the casing, annular segmental walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding reitbrt wall spaced from said non-heat conducting walls, said work-holding retort wall and said non-heat conducting walls forming between them a Continuous combustion space, means for supporting combustion in said combustion space whereby said work-holding retort wall is heated, and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort; said non-heat conducting wall disposed adjacent the base having 1ts inner annular edge beveled, and the lower edge ortion of the said work-holding retort eing correspondingly beveled, the two beveled portions cooperating with each other, to make an air-tight, close fit.

7. A furnace for carbonizing steel and like metals, including a curved outer casing, an

annular base member and top member fer said casing, a heat-resisting wall disposed within said outer casing and adjacent the inner surfaces of the base and top members, said heat-resisting wall adjacent the base and top members being annular in form, an inner work-holding retort Wall spaced from said heat-resisting wall, said work-holding retort being open at opposite ends, one end of which is supported upon the base member and the other end of which extends through the annular opening in the top member; a cover provided with a vent covering the open end of said work-holding retort; the outer "wall surface of said Workholding retort and the inner wall surface of said heat-conducting material forming between them a continuous combustion space, means for supporting combustion in said combustion space, whereby articles contained within said work-holding retort may be heated, and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort.

8. A furnace for carbonizing steel and like metals, including a curved outer casing, an annular base member and top member detachably joined to said casing, a portion of the inner edge surrounding the annular opening in said base being beveled, segmental walls composed of non-heat conducting material disposed adjacent the inner surface of the casing, annular segmental walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding retort wall spaced from said non-heat conducting walls, said work-holding retort wall and said non-heat conducting walls forming between them a continuous combustion space, means for supporting combustion in-said combustion space whereby said workholding retort wall is heated. and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort; a member provided with a central orifice and a beveled edge portion cooperating with the beveled edge portion of the base, and a protective plate provided with supports mounted above said orifice.

9. A furnace for carbonizing steel and like metals, including a curved outer casing, an annular base member and top member for said casing, a heat-resisting wall disposed within said outer casing and adjacent the inner surfaces of the base and top members, said heat-resisting wall adjacent the base and top members being annular in form, an inner work-holding retort wall spaced from said heat-resisting wall, said Workholdingretort being open at opposite ends, one end of which is supported upon the base member and the other end of which extends through the annular opening in the covering the open end of said work-holding retort; the outer wall surface of said work holding retort and the inner wall surface of said heat-conducting material forming between them a continuous combustion space, means for supporting combustion in said combustion space, whereby articles contained Within said work-holding retort may be heated, and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort; there being means mounted on the outer surface of the workholding retort; said outer casing wall and the heat-resisting wall having an opening communicating from said combustion space to the exterior'of the furnace, said opening having a progressively increasing diameter from the exterior of the furnace inwardly.

11. A furnace for carbonizing steel and like metals, including a curved outer casing, an annular base member and top member detachably joined to said casing, walls composed of non-heat conducting material disposed adjacent the inner surface of the casing, annular" walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding retortwall spaced from said non-heat conducting walls, said work-holding retort wall and said non-heat conducting walls forming between them a continuous combustion space, said outer casing wall and the non-heat conducting wall adjacent thereto having an opening communicating from said combustion space to the exterior of the furnace, said opening having a progressively increasing diameter from the exterior of the furnace inwardly; means associated with said openlng tor conveying means to support combustion 1n said combustion space whereby said workholding wall is heated,

and means for supplying a hydrocarbon fluid to thespace confined by said workholding retort. Y

12. A furnace for carbonizing steel and like metals, including a curved outer casing, an annular base member and top member detachably joined to said casing, walls composed of non-heat conducting material dis posed adjacent the inner surface of the easing, annular walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding retort wall spaced from said non-beat conducting walls, said work-holding retort wall and said non-heat conducting walls .forming between them a continuous combustion space, said outercasing Wall and the nonheat conducting wall adjacent thereto having openings communicating from said combustion space to the exterior of the furnace, said openings having progressively increasing diameters from the exterior of the furnace inwardly; means associated with said openings for conveying means to support combustion in said combustion space whereby said wor-k-holding retort wall is heated, and means for supplying a hydrocarbon fluid to the space-confined by said work- 'holdin retort.

13. furnace for carbonizing steel and like metals, including a curved outer casing, an annular base member and top member detachably joined to said casing, segmental walls composed of non-heat conducting ma terial disposed adjacent the inner surface of the casing, annular segmental walls composed of non-heat conducting material disposed adjacent the base and top members; an inner work-holding retort wall spaced from. said non-heat-conducting walls, said work-holding retort being open at opposite ends, one end of which is supported upon the base member and the other end of which-- extends through the annularopening in the top member, said opening in the base member communicating with the interior of the work-holding retort; the outer surface of said work-holding retort and the inner wall surface of said non-heat-conductingmaterial forming between them' a continuous combustion space, means for supporting combustion in said combustion space, whereby articles contained within said work-hold ing retort may be heated, and means for supplyin a hydrocarbon fluid to the space confined%oy said work-holding retort; a plate, provided with a circumferential lug, covering the annular opening of the base member; and means passing through the lug and into the base member for holding said plate detachably thereto.

14. A furnace for carbonizing steel andlike metals, including a curved outer casing,

an annular base member and top member deextends through the annular opening in the top member, said opening in the base member communicating withv the interior of the work-holding retort; th outer surface of said work-holding retort and the inner Wall surface of said non-heat conducting material forming between them a continuous combustion space, means for supporting combustion in said combustion space, whereby articles contained within said work-holding retort may be heated, and means for supplying a hydrocarbon fluid to the space confined by said work-holding retort; a plate, provided with a circumferential lug, covering the an- 15 nular opening of the base member, and

. Ima

a chambered portion having a central open' ing in the base thereof, and a side Wall of 20 said chamber being angularly disposed.

In testimony whereof, we have signed our names to this specification in the presence of two subscribing witnesses.

WILLIAM HOWARD FISHER. PETER CHAMBERS.

Witnesses JENNIE SHUTT, Jn CALVIN BROWN, 

